1. Field of the Invention
The present invention relates to an apparatus for cleaning a workpiece in the form of strips or sheets to be press-formed, to remove foreign matters from the workpiece prior to a press forming operation thereon.
2. Discussion of the Prior Art
Before a press forming operation is performed on a workpiece in a strip or sheet form prepared by cutting of a larger stock to desired size and shape, it is necessary to remove foreign matters such as dust and dirt, and particles produced by the cutting of the stock, which matters are deposited on or adhere to the surfaces of the workpiece. Otherwise, the foreign matters would mar or damage the workpiece during the pressing operation or cause defects on the product obtained from the workpiece. Usually, the stock to be cut into the workpiece strips or sheets is supplied or coated with a lubricant and/or an anti-rust oil during the cutting operation, and particles produced by the cutting operation and/or dust and dirt suspended in the ambient air are likely to adhere to the prepared strips or sheets. Therefore, the workpiece strips or sheets carrying such foreign matters are loaded onto a pressing machine or system. A cleaning apparatus to remove the foreign matters from successive workpiece strips or sheets should be adapted to clean the workpieces in synchronization with pressing cycles on the cleaned workpieces. In view of this requirement, there is widely used a cleaning apparatus of the type which uses brush rolls to brush the surfaces of the workpieces with a washing oil applied thereto while the workpiece strips or sheets are fed toward the pressing system. An example of such type of cleaning apparatus is disclosed in Publication No. 62-5877 of unexamined Japanese Utility Model Application.
Referring to FIG. 44, there will be described a known cleaning apparatus of the type as described above. This cleaning apparatus, which is indicated generally at 200 in this figure, is equipped with a belt feeder 202 which is adapted to feed workpiece strips 204 one after another, in the rightward direction as seen in FIG. 44. The cleaning apparatus 200 has a housing 206 with opposite end walls having an inlet and an outlet formed therethrough. The strips 204 enter and leave the housing 206 through these inlet and outlet, respectively. Within the housing 206, there are provided a pair of pinch rolls 208, a pair of brush rolls 210, a first pair of de-oiling rolls 212 and a second pair of de-oiling rolls 214, such that these pairs are arranged from the inlet toward the outlet in the order of description and such that the rolls of each pair are disposed one above the other. Strip guides 216 are provided between the adjacent pairs of rolls and at the inlet and outlet at the opposite ends of the housing 206.
The lower pinch roll 208 and de-oiling rolls 212, 214 are rotated clockwise at the same speed by a common drive motor (not shown), while the upper pinch roll 208 and de-oiling rolls 212, 214 are pressed against the lower rolls 208, 212, 214 by respective pneumatic cylinders (not shown), so that the strips 204 are fed in the rightward direction through the nips of the lower and upper rolls 208, 212, 214. The strips 204 leaving the outlet of the housing 206 are fed onto a loading station 218 of a pressing system in which the strips 204 are subjected to a predetermined pressing operation. The pair of brush rolls 210 are provided to brush and wash the upper and lower surfaces of each strip 204. Each brush roll 210 has a brush made of nylon, for example, on its circumference, which is forced onto the strip 204. The brush rolls 210 are rotated by a common motor (not shown) in a direction opposite to the feeding direction of the strip 204.
On the upstream and downstream sides of the pair of brush rolls 210, there are disposed a plurality of nozzles connected to a hydraulic circuit 220 for delivering a washing oil. The hydraulic circuit 220 has a clean oil reservoir 222 which stores the filtered washing oil, and a feeding pump 224 for pumping up the washing oil from the reservoir 222 and supplying the oil to the nozzles indicated above. The amount of delivery of the oil from the nozzles is adjustable by a regulating valve 226, while the flow rate of the oil is indicated by a flow meter 228. The operation of the feeding pump 224 is controlled on the basis of a moment at which each strip 204 is detected by a photoelectric tube 230 disposed on the belt feeder 202, so that the washing oil is supplied to the nozzles as long as the strip 204 is passing the nip of the brush rolls 210. The cleaning oil delivered from the nozzles is returned to a contaminated oil reservoir 234 through the bottom of the housing 206 and a filter 232. The washing oil overflowing the reservoir 234 is stored in an intermediate reservoir 236 and fed to a filtering device 240 by a filtering pump 238. The washing oil filtered by the filtering device 240 is supplied back to the clean oil reservoir 222 indicated above. The oil which overflows the clean oil reservoir 222 is stored in the intermediate reservoir 236.
A large amount of the washing oil remaining on the strip 204 after the washing of the strip 204 by the brush rolls 210 would cause an inadequate amount of tension on the strip 204 during a drawing operation on the strip 204 in the pressing system, whereby a product formed from the strip 204 would have a defect. To avoid this problem, the washing oil remaining on the brush-washed strip 204 is removed from the strip 204 by the de-oiling rolls 212, 214. These de-oiling rolls 212, 214 whose radially outer portion is made of an unwoven fabric and rotated in pressing contact with the surfaces of the strip 204, so that the residual washing oil is absorbed by the unwoven fabric of the rolls 212, 214.
However, the conventional method of washing the strips to remove the foreign matters by the brush rolls with a washing oil does not assure a sufficient cleaning effect when the feeding speed of the strip is relatively high. Further, the foreign matters such as dirt tend to easily adhere to the oil films covering the washed surfaces of the strips. There is also a risk that the foreign matters transferred to the brush rolls may be transferred back to the strips under washing. Although an increase in the amount of delivery of the washing oil would improve the washing effect, this solution would result in a failure of the de-oiling rolls to sufficiently remove the washing oil remaining on the strips. Thus, the amount of delivery of the washing oil has an upper limit.
Moreover, the conventional washing method deteriorates the operating environment due to scattering of the washing oil. In addition, the conventional method requires a considerably large reservoir and a filtering device, which are disposed in the ground, for receiving and filtering the contaminated oil. Thus, the conventional washing apparatus tends to be large-sized and require a considerably large installation space.
When strips of a relatively soft material such as aluminum strips or sheets to be formed into aluminum outer panels used on some motor vehicles of modern-vintage are washed by brush rolls as described above, the soft strips are likely to be marred, scratched or otherwise damaged by the brush rolls. Decreasing the force of the brush rolls acting on the strips would prevent such damage to the soft strips, but lead to an insufficient washing effect by the brush rolls.